The present invention relates to a method of preparing ductile material for processing in progressive dies and to manufactures associated with the method.
In the drawing of ductile metal sheet using progressive dies, a double-lanced suspension provides a blank whose structure can be progressively changed at different stations to form a press-drawn part. Connecting tabs maintain the location of the developing part on the sheet, so that the sheet can be moved to bring the developing part to the various stations containing the different tools of the die.
A commonly-used double-lanced suspension is initiated by slitting a sheet metal strip along circular arcs having two radii, one of an inner circle and one of an outer circle. The radius of the outer circle is only slightly larger than the radius of the inner circle.
Typically, two arcs are slit on the inner circle and two on the outer. The two arcs on the inner circle are opposite one another, and each arc may extend, for instance, 160-degrees, so that two oppositely lying, unslit, 20-degree segments remain. The two arcs on the outer circle are then centered on the 20-degree, unslit segments, and these two arcs may each extend 80-degrees.
U.S. Pat. No. 4,114,417 shows such double-lanced architecture at station 40b in its FIG. 5a. The same is shown in FIG. 12 of U.S. Pat. No. 4,291,567, while station 23 in FIG. 3 of U.S. Pat. No. 6,003,359 shows a doubling of the usual architecture. U.S. Pat. No. 4,114,417 is incorporated here in its entirety by reference, for the purpose of disclosing basic progressive-die, metal-drawing practice. U.S. Pat. No. 4,114,417 seems to be innacurate in its FIGS. 5a and 6a for not showing the gaps that occur at the sides of the blank as it is formed, but otherwise is good for its showing of the basic steps and progress in the forming of a part in progressive die practice.
It is an object of the invention to provide a ductile material processing method creating an improved double-lanced suspension.
Another object of the invention is the provision of manufactures exhibiting an improved double-lanced suspension.
These objects (as well as other objects which will become apparent from the discussions below) are achieved by:
a ductile material forming method including the steps of slitting a ductile material on two separated segments of an inner perimeter, thereby leaving two spacing zones on the inner perimeter, and slitting the material on two separated segments of an outer perimeter, the two segments of the outer perimeter deviating toward the two spacing zones of the inner perimeter; and
a manufacture including a blank of ductile material held to surrounding ductile material by four connecting tabs in two sets of two tabs each, the two tabs of a set extending toward one another, each from a surrounding-material-connected end to a blank-connected end, the blank-connected ends of the tabs of a set having a space between one another, the surrounding material protruding into said space.